Current profile method and apparatus for controlling gate operation

ABSTRACT

A method and apparatus for moving a gate a distance in a predetermined period of time. In one embodiment the current load for an electric motor to move a gate is first measured to determine whether the gate&#39;s motion is being hindered or helped. A microprocessor then controls voltage supplied to the motor to enhance or retard the evolved power of the motor according to the load and the predetermined time.

[0001] This is a continuation of copending application Ser. No.10/280,524 filed on Oct. 24, 2002.

FIELD OF THE INVENTION

[0002] This invention relates to powered gate openers and moreparticularly to regulating the power used to open and close poweredgates.

BACKGROUND OF THE INVENTION

[0003] Powered gates are frequently employed to move gates, such asthose which control access to a parking lot, to a gated community, or toprivate land, for example, by means of a power-drive unit which movesthe gate between open and closed positions. The gate may movehorizontally along a guide way or may swing about a vertical hinge axisto open and close the gate.

[0004] A typical power-drive unit for these gates includes an electricmotor mechanically coupled to a gate to cause the gate to move betweenopen and closed positions. The limits of movement of the gate itself areoften set by use of conventional limit switches or by simply timing thecycle of opening or closing by approximation. Alternatively, themechanism of the gate operator may be configured such that anapproximate opened and closed position for the gate is set by themechanical operation constraints of the mechanism itself.

[0005] The action of a gate through a cycle may also be controlled byuse of a microprocessor executing a program and controlling the powerunit. The term microprocessor is used herein by way of example to referto a programmable circuit having a memory, inputs and outputs and a CPU,or, an equivalent circuit. In this manner the power unit may be used tomore finely tune the motion of the gate to achieve a smoother cycle,avoid mechanical stresses to the gate, or otherwise program the actionof or access to the gate. Use of the microprocessor allows the powersupplied to the gate to be programmably varied during the cycleaccording to a calculated acceleration profile. Such a method andapparatus for moving a gate according to a calculated or predeterminedacceleration profile is disclosed in co-pending application entitledDYNAMIC ADJUSTMENT METHOD & APPARATUS FOR CONTROLLING GATE OPERATION, bythe same inventors and incorporated by reference herein.

[0006] It would be desirable to have a gate that completes an opening orclosing cycle each time in a predictable, set period of time. This ismost evident when multiple gates are used in tandem such as amaster/slave configuration.

[0007] A problem, however, arises when the gate is of a differentinertia or effective mass than that of one calculated by the programmingof the microprocessor, which might use a standard inertia or mass. Thismay be caused by many environmental variables, such as wind blowing withor against the opening gate, a child stepping on the gate for a ride,when dirt or ice is caught in the mechanism of the gate, etc. It canalso occur when the gate itself has been improperly mounted or hasbecome misaligned over time. The microprocessor, programmed to executean acceleration profile for a gate of a given mass, will take longer tocomplete a cycle when the gate has a heavier effective mass thananticipated. Likewise, the gate will complete the cycle more rapidlywhen the gate has a lighter effective mass than anticipated, for examplewhen it is being pushed by wind or out of plumb or on a downward slope.

[0008] Moreover, in some applications a microprocessor-controlledpowered gate may be moved according to an acceleration profile havingdifferent phases, the phases calculated to achieve a smooth action ofthe gate through the cycle. For example, a gate may be run throughacceleration, running and deceleration phases, which allow the gate tobe efficiently moved and come to a smooth stop. From this initialmeasurement of sampling an appropriate acceleration profile isdetermined to bring the gate from an initial position, throughacceleration, running and deceleration phases. This phased cyclingmethod is also predicated on an assumed mass for a gate and it isdesirable to cause the gate to complete the cycle of phases each time inthe same period of time.

SUMMARY OF THE INVENTION

[0009] A solution to the above problem has been devised. With a desiredtime to complete a cycle known, the effective inertia or mass of thegate is first measured upon initial movement of the gate. The output ofthe power unit can then be controlled by an acceleration profile variedto move the gate through the cycle in the desired time. This initialtest of the effective inertia or mass of the gate can be taken with eachinitiation of a cycle so that, for example, a gate stopped in mid-cyclewill reinitiate with the test when it is moved in an opposite direction.

[0010] Where the power unit is an electric motor, a measurement of thecurrent needed to power the motor correlates with the effective inertiaor mass of the gate. The desired cycle time, known output of the motorand the effective inertia or mass can then be factored to calculate anacceleration profile to be executed to cause the gate to complete itscycle within the desired time period.

[0011] This same method may be used with a phased cycle type ofacceleration profile. The phased acceleration profile may itself becalculated according to an initial measurement of the mass of the gate,then, further attenuated to cause the gate to complete all of thephases, the cycle, in the desired period of time.

[0012] For an electric motor, for example, the current needed by themotor to move a gate is proportional to the effective inertia or mass ofthe gate, a greater effective mass of the gate will require greatercurrent to move the gate. The microprocessor can then dynamicallyprogram the acceleration, running and deceleration phases through thecycle, determined by calculation from an algorithm or from a lookuptable, to achieve a completion of the cycle in the desired time.

[0013] A method for moving a powered gate through an opening or closingcycle in a predetermined period of time is disclosed that comprises thesteps of providing a gate that is mechanically connected to be moved bya power unit, wherein power to the power unit is regulated by amicroprocessor; providing power to the power unit and measuring thepower required of the power unit to move the gate; the apparent mass ofthe gate is then determined, based on the power drawn by the power unit.The gate is then accelerated and decelerated through an opening orclosing cycle based on an acceleration profile. The acceleration profileis either calculated by the microprocessor or by reference to a lookuptable stored in memory, by which the microprocessor receives appropriateinstruction as to how to move the gate through a cycle.

[0014] More specifically the microprocessor is used to determine anacceleration profile comprised of an acceleration phase, a running phaseand a deceleration phase that will move a gate of a given mass through acycle in a predetermined period of time. The power provided the powerunit, based on the measurement of the apparent mass of the gate, isattenuated to move the gate from a start position through theacceleration profile and complete the cycle to stop the gate at apredetermined end position. In most cases the acceleration phase and thedeceleration phase take a substantially equivalent period of time, butthis is not required.

[0015] In the preferred embodiment the power unit is an electrical motorand current provided to the electrical motor is regulated by amicroprocessor. Current is provided to the electrical motor and measuredby the microprocessor to determine a correlated apparent mass of thegate, and, current to the electrical motor is attenuated by themicroprocessor to move the gate through the acceleration profile.

[0016] The microprocessor may be use to determine the apparent mass ofthe gate by providing a predetermined speed parameter based on a knownmass of a gate. Electricity is supplied to the motor, and the currentdrawn from the motor is sampled a plurality of times to determine theload on the motor. The samples are then quantized and the used to arriveat an acceleration variable based on the samples. The speed of the motoris adjusted based on the acceleration variable, typically from the startposition to a predetermined end position through acceleration, runningand deceleration phases.

[0017] The present invention also encompasses an apparatus for moving apowered gate through an opening or closing cycle in a predeterminedperiod of time. A gate that is mechanically connected to be moved by apower unit and power to the power unit is regulated by a microprocessor.The power required to cause the power unit to move the gate is firstmeasured to determine a value proportional to the apparent mass of thegate, then the microprocessor determines an acceleration profile basedon the determined apparent mass of the gate. The microprocessor thenregulates the power to the power unit so that the gate is moved from astart position through the acceleration profile to stop the gate at apredetermined end position. This apparatus is further designed to beoperated according to the above methods of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a graph of comparative acceleration profiles for anexemplary gate of different effective masses, accelerated to complete acycle in the same period of time.

[0019]FIG. 2 is a graph of comparative acceleration profiles for anexemplary gate of different effective masses and cycling throughacceleration, running and deceleration phases, accelerated to complete acycle in the same period of time.

[0020]FIGS. 3a-3 e are graphs of the motion of a swing type gate as itis moved through the acceleration, running and deceleration phases ofFIG. 2.

[0021]FIG. 4 is a flow diagram of a method of the present invention.

[0022]FIG. 5 is a lookup table for use with the present invention.

[0023]FIG. 6 is a flow diagram of a method of the present invention.

DESCRIPTION OF THE INVENTION

[0024] The following detailed description, and the figures to which itrefers, are provided for the purpose of describing examples and specificembodiments of the invention only and are not intended to exhaustivelydescribe all possible examples and embodiments of the invention.

[0025] Referring now to FIG. 1, a graph of different accelerationprofiles used for a gate to complete a cycle of the same desired time isshown. At the start, T₀ (time=0), the gate is at rest. At period T₀-T₁,the breakaway phase, an electric motor whose characteristic power outputand current requirements are known is given a command to accelerate agate of known mass to a known speed or to maximum speed. The currentdrawn by the motor is measured and used by the microprocessor executingthe program to calculate the effective inertia or mass of the gate. Oncethe effective inertia or mass of the gate is determined, an accelerationprofile can be calculated to move the gate through its cycle in thedesired time period to the endpoint T₄.

[0026] The acceleration profiles of a gate having three differenteffective masses are shown. A heavier gate, line H, is accelerated for alonger period of time to allow it to reach the end point at the end ofthe desired time period. A lighter gate, line L, is under-accelerated ordecelerated sooner to delay it in order to reach the end point at theend of the desired time period. The lighter gate in this example isaccelerated less and moved at a slower constant speed after accelerationto cause it to complete the cycle in the desired amount of time. In allcases a combination of attenuating the acceleration and constant speedof the gate are combined to cause the gate to complete the cycle in thedesired time.

[0027] Referring now to FIG. 2, a graph is shown of the comparativeacceleration profiles of another method of the present invention. Thismethod is employed when a gate using an acceleration profile includingacceleration, running and deceleration phases is used. By way of examplea swing type gate may be moved through an opening or closing cycle asshown at FIGS. 3a-3 e. A graph of time vs. velocity of the gate, thecorresponding respective positions of the swing-type gate during thesephases are detailed in FIGS. 3a-3 e, for example, in about ten seconds.

[0028] At the start, T₀ (time=0), the gate is at rest (corresponding toFIG. 3a). From period T₀-T₂, (corresponding FIGS. 3a and 3 b) the gateis in the acceleration phase and is accelerated to a running speed,shown as line segment M. Period T₀-T₁ (corresponding FIG. 3b) is thebreakaway phase, the initial part of the acceleration phase where thecurrent drawn by the gate is measured to determine the accelerationprofile of the remainder of the cycle. Period T₁-T₂ (corresponding toFIG. 3c) is the is the acceleration phase exclusive of the breakawayphase. The T₂-T₃ period (corresponding FIG. 3d) is the running phase,where the motor drives the gate at a speed that is either limited to agiven speed or represents the maximum output of the electric motor.Period T₃-T₄ is the deceleration phase, the deceleration beginning at T₃This deceleration phase slows the gate to allow for a smooth closure atthe end position T₄.

[0029] For comparison purposes the acceleration of a lighter gate isshown as line L in FIG. 2, with a standard gate shown as line S and aheavier gate shown as line H. In this example the lighter gate has asteeper acceleration and deceleration curves for gate movement, i.e. thelighter gate reaches running speed more quickly, shown at T₂′. Becausethis gate is effectively lighter the running speed is slowed so that itwill be delayed just long enough to complete the cycle in the desiredtime. For a heavier gate more time is needed to bring the gate torunning speed, so the running speed during the running phase isincreased just enough to cause the gate to complete the cycle in thedesired time.

[0030] In all cases a combination of attenuating the accelerationperiod, the constant speed and the deceleration period of the cycle areused to cause the gate to complete the cycle in the desired time.

[0031] A broad aspect the method of the present invention is show inFIG. 4. Parameters are known for the electric motor used such as thepower output of the motor being used and the proportional current drawnby the motor for a given delivered power output. Also known is thedistance the gate must travel during the cycle are known and the desiredtime to complete the cycle.

[0032] In the breakaway phase the electric motor is supplied withcurrent and the current is measured. The correlation between the currentused and the power needed to drive the gate may be inferredmathematically. The effective inertia or mass of the gate may then beinferred mathematically from the power needed to move the gate. Anacceleration profile is then calculated and executed by themicroprocessor, regulating the electric motor to cause it to move thegate to complete the cycle in the desired time.

[0033] The amount of power needed by an electric motor can be calculatedbecause a conductor immersed in a magnetic field will produce a force(F) that can be calculated as a product of the magnetic flux density(B), the current (I) through the conductor and the length of theconductor (L):

F=B*I*L

[0034] A similar effect occurs when the conductor is moved at certainvelocity (v) through a magnetic field (B). A voltage (E) is generated atbetween the ends of the conductor based on the following formula:

E=−B*L*v

[0035] Motion in an electric motor is achieved by applying an electriccurrent to the winding and, as a result of the motion, a voltage will begenerated. This voltage generation (E) will always oppose the flow ofthe applied current. In an electric motor the conductor takes the formof coiled turns. The torque (T) developed on each turn of such coil isoften alternately expressed as a function of the current (I) and thevelocity (v) of the moving conductor:

T=I*v

[0036] In an electric motor the velocity is actually expressed asangular velocity because the winding conductor is circular and isrotating inside of the magnetic field, the above formula can beexpressed as:

T=I*dλ/dO  (1)

[0037] Where dλ is the magnetic flux linking the winding and d0 is theangular displacement.

[0038] In the same way, the voltage generated in each turn of windingcould be expressed as being fully proportional to the velocity, in thiscase:

E=dλ/dO=angular velocity  (2)

[0039] The normal way to apply current through a conductor is byapplying voltage across the ends of the conductor. Upon the applicationof a voltage motion will result as the current flows and a voltage (E)will be generated as the conductor moves. An electrical model todescribe this behavior a formula for an electric motor is:

V=RwI+KeW  (3)

[0040] Where V=Voltage applied to the motor (or conductor wire,winding); Rw=Equivalent resistance of the conductor (in this case thecurrent carrying element of the winding resistance); Ke=voltage constantempirically measured for a given motor winding; W=angular speed of theshaft of the motor, and I=current through the conductor winding.

[0041] The force or torque required to create motion by an electricmotor can be determined by taking into account that the current (I) isproportional to the torque by the angular displacement as coefficientfrom equation 1. If a linear relationship between the current (I) andthe torque (T) is desired the coefficient in this equation must remainconstant, which is to say that the angular displacement must remainconstant.

[0042] To keep the angular displacement constant in an electric motorthe voltage is kept constant, as shown in equation 2. Keeping thevoltage (V) constant will cause a constant angular displacement andtherefore will cause a linear relationship between the torque generatedby the motor, creating gate motion, and the current through the windingof the motor.

[0043] Measuring the current of an electric motor to determine the loadon an electric motor can be done in many different ways. In thepreferred embodiment a integro-differential analysis is used to quantizethe current and therefore the load on the motor. This is performed bythe utilization of an analog to digital (A/D) converter as a transducerbetween a current sensor and the microprocessor unit.

[0044] In the preferred embodiment the microprocessor unit samples thecurrent for a pre-determined time period, expressed as:

L(n)=I(n)| from t0-tx

[0045] Where t0=start time of capturing one or more current samples;tx=end time of capture of samples; I(n)=the quantized value of the motorcurrent sample at t0-ts, where ts=interval of time between samples andts<=tx; n=number of samples such, and N=maximum number of samples.

[0046] This is the equivalent of:

L1=I(dλ/dO)*T(n)

[0047] Again, d/dO is the angular displacement, so dλ/dO=Kv*V where Kv=avoltage constant and V=voltage applied to the motor.

[0048] Therefore:

I1Kv*V*T(n)

[0049] If a constant voltage is applied to the motor then: L1=I1Kvt*T(n)so that the quantization of the current is a representation of thetorque or force to create motion. Because, in the present invention, theload is the actual gate along with the middle interconnection elementssuch gear boxes, pulleys, arms, friction between parts and the like, wecan say then that the system comprising the gate and the interconnectionelements required to move the gate create a load on the motor accordingto:

I=Kg*Wg

[0050] where Kg=relation between the motor shaft load and effective loadto move the gate and Wg=is a quantization value of the effective torqueor force to move the gate at a sampling point.

[0051] Therefore L1 can be expressed as function of the gate systemsitself:

L=(Kvt/Kg)*Wg(n)

[0052] Where Kvt=product of the voltage constants, angular speed andcurrent and torque; IS THIS RIGHT? Kg=relation between the motor shaftload and effective load to move the gate, and Wg(n)=quantization valuesof the effective torque or force to move the gate at sampling points n.

[0053] The quantization values of the motor current as described aboverepresent the force required to move a gate element, in other words wecan determine how “heavy” or “light” is the “gate” and act accordingly.

[0054] The current measured is therefore is proportional to a giveneffective inertia or mass of the gate. Once the effective inertia ormass is known the acceleration profile for a phased or non-phasedaccleration profile can be attenuated to cause the gate to complete itscycle in the desired time.

[0055] Although the methods of the present invention are exemplified foran electric motor, this method may also be used with other power units,such as an internal combustion engine. In the case of a non-electricpower unit the effective torque on the power unit is measured during thebreakaway phase.

[0056] Once the effective inertia or mass of the gate is known themicroprocessor may use a lookup table stored in memory to determine anappropriate acceleration profile, an exemplary lookup table is shown inFIG. 5,

[0057] The lookup table may used for both phased and non-phasedacceleration profiles, for a phased cycle to determine the appropriateperiods for the acceleration, running and deceleration phases.

[0058] Alternatively, in the preferred embodiment the microprocessor isprogrammed to fully calculate an appropriate acceleration profiledepending on the gate usedthrough the use of a lookup table comprisingeither predetermined profiles or coefficients in which the idealizedprofile is modified to account for the effective mass of the gate. Inthe method of the preferred embodiment, as shown in the flow diagram ofFIG. 6, an acceleration profile for a given condition is determined byfirst programming the microprocessor to move the gate at an initialspeed, during the breakaway phase, at an initial speed parameter. Themotor is then run, during a breakaway phase and the current draw of themotor is sampled. One or more samples may be taken until an accuratesampling has been achieved.

[0059] The samples are then quantized as outlined above to arrive at anacceleration variable according to the method above. Finally theacceleration profile, the acceleration, running and deceleration phasesis selected or calculated and the gate is moved through thatacceleration profile in the desired time by adjusting the current to theelectric motor.

[0060] It will be appreciated that the invention has been described hereabove with reference to certain examples or preferred embodiments asshown in the drawings. Various additions, deletions, changes andalterations may be made to the above-described embodiments and exampleswithout departing from the intended spirit and scope of this invention.Accordingly, it is intended that all such additions, deletions, changesand alterations be included within the scope of the following claims.

What is claimed is:
 1. A method for moving a powered gate through anopening or closing cycle in a predetermined desired time periodcomprising the steps of: a) providing a gate that is mechanicallyconnected to be moved by a power unit, wherein power to the power unitis regulated by a microprocessor, b) providing power to the power unitand measuring the power required of the power unit to move the gate, c)executing a program with the microprocessor to determine the effectiveinertia or mass of the gate based on the power drawn by the power unit,d) further executing the program with the microprocessor to determine anacceleration profile calculated to move the gate from a start positionto a predetermined end position in a predetermined desired time, and, e)executing the program to attenuate the power provided the power unit tocause the gate to move from the start position to the predetermined endposition in the desired period of time.
 2. The method of claim 1 whereinthe acceleration profile is determined by mathematically calculating anacceleration profile.
 3. The method of claim 1 wherein the accelerationprofile is determined by referring to a lookup table.
 4. The method ofclaim 1 wherein the power unit is an electrical motor and the powerprovided is electrical current provided to the electrical motor that isregulated by the microprocessor, current is provided to the electricalmotor and measured by the microprocessor to determine a correlatedeffective inertia or mass of the gate, and, current provided to theelectrical motor is attenuated by the microprocessor to move the gatethrough the acceleration profile.
 5. The method of claim 4 wherein theeffective initial inertia or mass is determined by: a) supplyingelectricity to the motor, b) sampling the current drawn from the motorone or more times to determine the load on the motor, d) quantizing thesamples, e) determining an acceleration variable based on the samples,and d) adjusting the speed of the motor based on the accelerationvariable.
 6. The method of claim 5 wherein the acceleration profile isdetermined by mathematical calculation by the microprocessor, withoutreference to a lookup table.
 7. The method of claim 5 wherein theacceleration profile is mathematically calculated by the microprocessorusing a lookup table for reference.
 7. The method of claim 1 wherein themicroprocessor further determines an acceleration profile having anacceleration phase, a running phase and a deceleration phase.
 8. Themethod of claim 7 wherein the acceleration phase and the decelerationphase take a substantially equivalent period of time.
 9. The method ofclaim 7 wherein the acceleration phase and the deceleration phase takedifferent periods of time.
 10. An apparatus for moving a powered gatethrough an opening or closing cycle in a predetermined period of time,comprising: a gate that is mechanically connected to be moved by a powerunit, wherein power to the power unit is regulated by a microprocessor,the power required to cause the power unit to move the gate is firstmeasured to determine a value proportional to the effective inertia ormass of the gate and the microprocessor determines an accelerationprofile based on the determined effective inertia or mass of the gate tomove the gate from a start position through the acceleration profile tostop the gate at a predetermined end position in a predetermined periodof time, and the microprocessor can regulate the power to the power unitso that the gate is moved from a start position through the accelerationprofile to stop the gate at a predetermined end position.
 11. Theapparatus of claim 10 wherein the acceleration profile is determined bymathematically calculating an acceleration profile.
 12. The apparatus ofclaim 10 wherein the acceleration profile is determined by referring toa lookup table.
 13. The apparatus of claim 10 wherein the power unit isan electrical motor and the power provided is electrical voltage to theelectrical motor that is regulated by the microprocessor, current isprovided to the electrical motor and measured by the microprocessor todetermine a correlated effective inertia or mass of the gate, and,voltage provided to the electrical motor is attenuated by themicroprocessor to move the gate through the acceleration profile. 14.The apparatus of claim 13 wherein the effective initial inertia or massis determined by: a) supplying electricity to the motor, b) sampling thecurrent drawn from the motor one or more times to determine the load onthe motor, d) quantizing the samples, e) determining an accelerationvariable based on the samples, and d) adjusting the speed of the motorbased on the acceleration variable.
 15. The apparatus of claim 14wherein the acceleration profile is determined by mathematicalcalculation by the microprocessor, without reference to a lookup table.16. The apparatus of claim 14 wherein the acceleration profile ismathematically calculated by the microprocessor using a lookup table forreference.
 17. The apparatus of claim 10 wherein the microprocessorfurther determines an acceleration profile having an acceleration phase,a running phase and a deceleration phase.